This invention relates to a device for infusing a therapeutic agent to a desired site within a patient or withdrawing a fluid from a patient, and more particularly, to such a device which is implanted such that no portion is transcutaneous. Its access portion is subcutaneous but designed so as to facilitate repeated access by the percutaneous route.
In current human and animal medical practice, there are numerous instances where therapeutic agents must be delivered to a specific organ or tissue within the body. An example is the infusion of chemotherapy into a central vein on a recurring basis over a lengthy treatment period for widespread sites of malignant tumor. Without an infusion device for intravenous drug infusion, multiple vein punctures over a lengthy period results in progressive thrombosis, venous sclerosis, and destruction of small diameter peripheral vessels. In other cases, it may be desirable to infuse chemotherapy to a localized malignant tumor site. It may be difficult or impossible to deliver an agent specifically to such a site on a regular repetitive basis without surgically implanting an infusion system. Similarly, repeated arterial access is occasionally needed for injection of an X-ray dye or contrast agent into an artery for diagnostic purposes. In other situations, there is a need to remove a body fluid repetitively for analysis from a remote body site. Finally, sensing and physiological measuring devices incorporated into small diameter catheters and small diameter optical fibers are increasingly being utilized for monitoring body processes and could be more easily implemented through a properly designed access device with an adequate internal diameter.
In prior medical practice, percutaneous catheters have been used to provide vascular or organ access for drug therapy or removing body fluids. Although such systems generally performed in a satisfactory manner, numerous problems were presented by such therapy approaches, including the substantial care requirements by patients, e.g. dressing changes with sterile techniques, a significant rate of infection of the catheter because of its transcutaneous position, and a high rate of venous thrombosis, particularly if the catheter was located within an extremity vein.
Implantable infusion devices or "ports" have recently become available and are a significant advance over transcutaneous catheters. Presently available infusion ports have a number of common fundamental design features. The ports themselves comprise a housing which forms a reservoir which can be constructed from a variety of plastic or metal materials. A surface of the reservoir is enclosed by a high-density, self-sealing septum, typically made of silicone rubber. Connected to the port housing is an outflow catheter which communicates with a vein or other site within the patient where it is desired to infuse therapeutic agents. Implantation of such devices generally proceeds by making a small subcutaneous pocket in the patient under local anesthesia. The internal outflow catheter is tunneled to the desired infusion site and is connected to the infusion port. When the physician desires to infuse or remove material through the port, a hypodermic needle is used which pierces the skin over the infusion port and is placed into the port.
Although presently available implantable infusion ports generally operate in a satisfactory manner, they have a number of shortcomings. Since these devices rely on a compressed rubber septum for sealing, there are limitations in the diameter of needles which can be used to penetrate the septum, since large diameter needles can seriously damage the septum. Moreover, the needles used must be of a special design which minimizes septum damage. These diameter limitations severely restrict the flow rate of fluids passing through the port.
For prolonged infusion using a conventional port, the infusion needle is taped to the patients skin to hold it in position. Conventional ports do not allow the needle to penetrate deeply into the port so that a small displacement of the needle can cause it to be pulled from the port. In cases where locally toxic materials are being infused, extravasation of such materials can cause local tissue damage which can lead to a requirement for corrective surgery such as skin grafting or removal of tissue.
Presently available implantable drug infusion devices must also have a significant size to provide an acceptable target surface area for the physician who must locate the port and penetrate the septum properly with a needle. The port housing becomes bulky as the septum size increases since structure is required to maintain the septum in compression to provide self-sealing after the needle is removed. Moreover, presently available infusion ports are difficult to clear if thrombosis occurs within them or in the implanted outflow catheter, since it is difficult if not impossible to feed a cleaning wire through the penetrating hypodermic needle in a manner which will clear the infusion device and the internal outflow catheter. Present infusion ports have a retained volume beneath the self-sealing septum which increases the volume of drug which must be administered to enable a desired quantity to reach the infusion site. This retained volume also poses problems when a physician desired to deliver different drugs to the same infusion site which are incompatible when mixed. In addition, when it is desired to withdraw blood through the port, the retained volume of the prior art infusion ports is an area where blood clotting can occur, thus interfering with future access to the site. And finally, for present infusion ports, there is a risk that the physician attempting to pierce the port septum will not properly enter it, leading to the possibility of extravasation which can cause significant undesirable consequences as mentioned previously.
The present invention relates to an implantable infusion port which provides numerous enhancements over prior art devices. In accordance with this invention, an infusion port is provided which incorporates the funnel-shaped entrance orifice which narrows down to a reduced diameter guide passageway. The guide passageway terminates at an internal cavity which retains an articulating catheter valve such as a multi-element leaflet valve assembly. The port also has an exit passageway which connected to an implanted outflow catheter. The infusion port of the present invention is adapted to be used in conjunction with a sharp hypodermic access needle of conventional design which may be used by itself for infusion or fluid withdrawal, or with an external inflow catheter having the needle fed through it (or vise versa) allowing a catheter to be put in position within the infusion port or fed into the implanted catheter for infusion or withdrawal of fluid. The entrance orifice guides the needle to the guide passageway. The reduced diameter guide passageway of the port housing accurately aligns the access needle to strike the catheter valve at a desired area so that a needle can be used to penetrate the catheter valve repeatedly without impairing the function of the valve. Various forms of articulating catheter valves can be employed in connection with the present invention. One such valve is a leaflet valve having one or more flat discs of an elastomeric material having cuts through them to define leaves or flaps which normally resist the flow of fluids across the valve, but can be penetrated by a sharp access needle.
Use of the embodiment of this application differs from those of the parent application in that it is primarily intended to be used with a sharp access needle as compared with the embodiments of the parent application which are intended to be used with a blunt accessing instrument.
The convenient access to the port and internal outflow catheter provided by this invention enables these elements to be cleared with a wire, avoiding the problem of permanent impaction of prior art devices. In addition, the ability to feed a guide wire into the infusion port and internal catheter of this invention enables the internal catheter to be repositioned using a bent or "steerable" guide wire.
The infusion ports having an articulating catheter valve of this invention possess the advantage that they have a very small reservoir or "dead space", meaning that virtually all of the infused fluid is throughput to the desired infusion site. This invention, therefore, facilitates infusion of incompatible materials in a serial fashion since very little of the previously infused fluid remains in the device when a subsequent infusion is carried out. The port of this invention also permits an introduced catheter or other filament to be deeply inserted into the internal outflow catheter which reduces the possibility of small displacement of the introduced filament causing it to be from being withdrawn from the port during infusion.
Additional benefits and advantages of the present invention will become apparent to those skilled in the art to which this invention relates from the subsequent description of the preferred embodiments and the appended claims, taken in conjunction with the accompanying drawings.